Ergonomic chair

ABSTRACT

An ergonomic chair provides continuous support to the seated user throughout a broad range of postures by pivoting both the seat and back supporting cushions about a first or common axis disposed above the seat support cushion and in front of the back support cushion. The back supporting portion also independently pivots about a second horizontal axis proximate the lumbar region in a manner that allows the back supporting cushion to assume an angle that provides permanent contact with the seated user&#39;s back when said user is leaning back against the back support cushion. The springs that otherwise oppose the free rotation about the first and second axis are balanced such that the force inherently exerted by the user during movement through a range of seated postures is sufficient to initiate the coordinated rotation of the seat and back supporting element. No additional exertion is required once the user has reached the desired inclination, as the return springs are selected to counterbalance the redistributed weight of the user. Thus, full contact of the back supporting portion with the user&#39;s back is achieved over a full range of postures to provide proper ergonomic support, allowing the user to stay at task. In combination with such motion, which maintains the head at a level and angle such that the eyes can remain focused on their primary visual target without need to adjust the height, depth or angle of the target. The chair can offer armrests that support the forearms of the seated user to reduce the load carried by the arms, shoulders, neck and back and cooperate with the motion of the seat and back supporting elements to maintain ergonomically correct orientation of the hands to the keyboard or work surface.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to the provisional application having Ser. No. 60/617,540 entitled “Ergonomic Chair” filed on Oct. 8, 2004, which is incorporated herein by reference.

BACKGROUND OF INVENTION

The present invention relates to improved seating, and in particular improved task seating.

Numerous improvements and innovations have been made to conventional chairs for the purposes of providing more comfortable and ergonomically correct seating for office and factory workers, as well as others required to sit for long periods of time.

However, despite these improvements seated workers are subject to repetitive strain injuries to extremities, discomfort and stiffness because, in part their posture is either incorrect or limited. While many modern office chairs provide for adjustability of the seat height, back support tilt, seat tilt and armrests the inherent complexity in these mechanisms dissuades their deployment to the user's full benefit.

It is therefore a first object of the present invention to provide an ergonomically improved chair that reduces stress on the body.

It is a further objective of the invention to provide an ergonomically improved chair that automatically adjusts to suit each user.

It is an additional object of the invention to provide an ergonomically improved chair that allows unrestricted movement through a greater range of ergonomically correct postures.

It is another object of the invention to provide an ergonomically improved chair that allows a user to stay at task through a greater range of postures.

SUMMARY OF INVENTION

In the present invention, the first object of improved worker/user comfort and reduced ergonomic hazards is achieved by providing a chair comprising a frame supported on a surface, the frame having a forked armature extending upward there from, a seat support mounted in suspension about a first rotary axis from the forks of said frame, a U-shaped mounting bracket having a left and right terminus, each of which is disposed in rotary connection about the forks of the armature and in substantial coincidence with the first rotary axis, and a back support cushion disposed between the left and right terminals of said U-shaped back support, being mounted to pivot thereon about a second rotary that is located behind the back support cushion and proximate the lumbar spine region of the seated user. The rotation of seat support and back cushion support about the first and second axis enable the seated user's unrestricted movement to any posture within the range of seated postures recommended by the American National Standards Institute and the Human Factors and Ergonomics Society. Further, the user is free to stretch and flex yet is stably supported without the need to operate controls.

Another object of the invention that reduces the ergonomic hazards thought to increase the risk of injury is that at any posture the user assumes (and at any point in the movement between those postures) the back support cushion maintains permanent contact with the seated user's back and especially the lumbar spine.

The additional object of the invention of reducing the risk of ergonomic hazards is achieved by keeping the seated user's hands in proper orientation to their task during movement by means of an armrest that maintains the user's hands in an ergonomically correct orientation to the tool or work surface, that is, the armrest does not change its position as the user moves through the range of available postures. This is further improved by utilizing a double pivot freely rotating armrest to increase the horizontal range of the arm support. This aspect is further achieved in preferred embodiments by providing at least one auxiliary support surface disposable within an ergonomic position by rotation about the vertical arm rest support, the support surface being suitable for support of a keyboard, mouse, trackball, microscope or other requisite tool, and the like.

Further, the primary visual target does not need to be repositioned as the head only moves a small distance by the allowed pivotal rotation between inclined and reclined postures.

The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of the embodiments thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a perspective drawing of the ergonomically improved chair of the present invention.

FIG. 1B is an elevation of a user seated in the chair in a first position

FIG. 1C is an elevation of a user seated in the chair in an alternative position

FIG. 1D is an elevation of a user seated in the chair in an alternative position

FIG. 2A is plan view of the chair of FIG. 1

FIG. 2B is a front elevation of the chair of FIG. 1

FIG. 2C is a side elevation of the chair of FIG. 1 orthogonal to the elevation of FIG. 2B.

FIG. 3 is a perspective drawing of the rear of the chair of FIG. 1 showing the assembly of the back support cushion to the U-shaped mounting bracket.

FIG. 4A is detailed side elevation showing the assembly of the back support cushion to the U-shaped mounting bracket. FIG. 4B is the side view of the completed assembly of FIG. 4A in an alternative position when the back support cushion is tilted backward as the user leans back in the chair.

FIG. 5A is detailed side elevation showing an alternative embodiment of the assembly of the back support cushion to the U-shaped mounting bracket wherein the pivoting movement of said back support cushion about the second rotary axis is opposed by a tension spring. FIG. 5B is the side view of the completed assembly of FIG. 5A in an alternative position when the back support cushion is tilted backward as the user leans back in the chair.

FIG. 6A is a perspective illustration showing further details of the return spring mechanism associated with the chair seat support and the tension adjustment of the return spring.

FIG. 6B is a cutaway view of those parts mounted to the common swing support.

FIG. 7A is a plan view of an auxiliary support tray engaged in the in use position

FIG. 7B is a plan view of the auxiliary support tray of FIG. 7 engaged in the stored position.

FIG. 8A is an elevation of a preferred embodiment of the chair showing the armrest in the most forward extended position.

FIG. 8B is an elevation showing an alternative position of the armrest of FIG. 8A in the most withdrawn position.

DETAILED DESCRIPTION

Referring to FIGS. 1 through 8, wherein like reference numerals refer to like components in the various views, there is illustrated therein a new and improved Ergonomic Chair, generally denominated 100 herein.

In accordance with the present invention FIG. 1A illustrates a chair 100 having a frame 105 that is supported by a horizontal supporting base section 106, and a vertical post 115 extending upward there from. Frame 105 includes a forked armature 110 with the arms of the fork extending upward. The seat support 120 is suspended from the terminals of fork arms by a pair of swing arms 121 and 121′ that rise vertically from opposing sides of the seat support to define a first rotary axis 210. The swing arms 121 rotate about rotary coupling 150. Alternatively, the seat support may be suspended with the trough of a U-shaped brace, with the arms or upright section of the U-shape corresponding to swing arms 121 and 121′.

Further, a U-shaped mounting bracket 130 is disposed in rotary connection about the forks of the armature about left 131 and right terminus 132, the axis of rotation being the same or in substantial coincidence with the first rotary axis 210. When the axis of rotation of the forked armature and the U-shaped mounting bracket coincide, it is preferable that they rotate by means of a common rotary coupling 150.

A back support cushion 140 is disposed between the left 131 and right 132 terminals of the U-shaped mounting bracket 130, being mounted to pivot thereon about a second rotary 220, shown in FIG. 2. Back support cushion 140 preferably has a curvilinear bulge 141 extending outward toward the front of the seat and intended to be coincident with the lumbar spine region of the seated user. The back 142 of seat cushion 141 is connected to the U-shaped mounting bracket 130 at hinge 155. Thus, the placement of the axle of the hinge defines the vertical and horizontal disposition of the second rotary axis 220 as located behind the back support cushion.

It should be appreciated that in alternative embodiments of the invention the position of the seat can be adjusted with respect to that of the back support without varying or changing their respective axis of rotation. Alternatively, in other embodiments either seat or the back support can be displaced horizontally from their respective axis of rotation.

Preferably base 106 of frame 105 includes a plurality of legs 107 as shown in FIG. 1 and FIG. 3, with a roller ball 108 mounted to the end of each leg (FIG. 3). However, it should be appreciated that in other applications, such as theatre or airplane seating it is preferable that the frame is fixed to the flooring or ground. In office or desk application it is also preferable that vertical post 115 includes a height adjustment means to modify the height of seat support 120 from the floor or frame supporting surface.

In more preferred embodiments, the chair 100 also includes arm supports 111 and 111′ mounted proximate to or on the left 131 and right terminus 132 of forked armature 110. More preferably the armrests, like the seat support and back support are cushioned surfaces.

In other preferred embodiments, the armrest supports 111 and 111′ and associated cushions are attached to the frame via height adjustable pivoting means such that the armrest cushions can remain in a fixed horizontal position as the seat 120 and/or back support cushion 140 pivot about the first 210 and second 220 rotary axis.

In the more preferred embodiments, described in further detail with respect to FIG. 8, the armrest supports 111 and 111′ undergoes a wide range of motion and extension by a double pivoting mechanism, and are thus readily translated in a common plane via frictional contact with the user's forearms, thus continuing to support the user's forearms irrespective of their tilt in the chair 100 or the movement of their hands to new manual targets, for example movement between keyboard and mouse.

FIGS. 1B, C and D illustrate the position of the seat 120 and back supporting 130 components of the chair with respect to the user's body, and in particular the contact with the spine or lumbar region as the user is in the nominal seated position (FIG. 1B), leans forward (FIG. 1C) or reclines (FIG. 1D). It should be noted that the ergonomic chair provides continuous support to the seated user throughout a broad range of postures by pivoting both the seat and back supporting cushions about a first 210 or common axis disposed above the seat support cushion and in front of the back support cushion. The back supporting portion also independently pivots about a second horizontal axis 220 proximate the lumbar region in a manner that allows the back supporting cushion to assume an angle that maintains permanent contact with the seated user's back when said user is leaning back against the back support cushion. Thus, full contact of the back supporting portion with the user's back is achieved over a full range of postures to provide proper ergonomic support, allowing the user to stay at task and reducing the incidence of sitting in an unsupported position.

FIG. 3 is a perspective drawing of the rear of the chair of FIG. 1 showing one possible assembly of the back support cushion to the U-shaped mounting bracket. U-shaped mounting bracket 130 has a substantially rectangular plate 135 disposed at the rear of the U-shape, with a vertically oriented slot 136 therein. The rear of support cushion 140 has a hinge 155 with a rotary axis disposed horizontally to connect a support plate 154. A threaded post 153 extends outward orthogonal to support plate 154 and is inserted through slit such that the attachment of knob 137 secure the seat back cushion 140 to the U-shaped support brace 130. Alternatively, the back support 140 can be attached to the U-shaped mounting bracket 130 by alternative combinations of a knob and screw type fixture, as described with respect to FIGS. 5A and 5B.

It should be appreciated that the position of the lumbar bulge 141 can be modified to accommodate users of different heights simply by raising or lower the height of back support 140 by translating the position of threaded post 153 in slot 136.

As further illustrated in FIGS. 4, 5 and 6, return springs that otherwise oppose the free rotation about the first 210 and second axis 220 are balanced such that the force inherently exerted by the user during movement through a range of seated postures is sufficient to initiate the coordinated rotation of the seat and back supporting components. Thus, no additional exertion is required once the user has reached the desired inclination, as the return springs are also selected to counterbalance the redistributed weight of the user. The term return springs is intended to encompass such alternatives as compression springs, tensile or tension springs, torsion springs, airs bladder or the friction between mating surfaces, and the like. Springs may include, but are not limited to metal coils or an elastic rubber block.

FIG. 4A is detailed side elevation showing the assembly of the back support cushion to the U-shaped mounting bracket. Torsion return spring 156 is mounted about the axis of hinge 155 to urge the support plate 154 and mounting plate 157 together in the absence of a load being applied to the back support cushion by the user, the orientation shown in the figure. However, as shown in FIG. 4B, when the user leans backward against seat support cushion 140 hinge 155 is opened as the force of torsion return spring 156 is overcome.

A preferred spring is a tension spring that reacts when the user leans back the tension spring stretches as the support plate 154 and mounting 157 move apart. FIG. 5A is detailed side elevation showing the assembly of the back support cushion to the U-shaped mounting bracket when the return spring 156 is a tension spring mounted below axis of hinge 155 to urge the support plate 154 and mounting plate 157 together in the absence of a load being applied to the back support cushion by the user, the orientation shown in the figure. However, as shown in FIG. 5B, when the user leans backward against seat support cushion 140 hinge 155 is opened as the force opens tension spring 156. the preferred form of a tension spring is a rubber elastic block.

It has been discovered that significant ergonomic improvement is obtained in any chair comprising the mechanism shown in FIGS. 5A and 5B wherein a tension spring opposes the pivoting movement of the back support portion or cushion, and in particular when the rotary or pivot axis is located behind the back support cushion and proximate the lumbar spine region of the seated user. The back rest or back rest cushion may recline independent of the seat. The tension spring 156 stores energy as the user reclines, this energy then assists the user in coming out of the recline. The position of the hinge point can help provide continuous lumbar support during recline, as it also affects the power of the spring as it increases the leverage. Preferably, the backrest for the chair includes a rotary mount attached to said back support surface enabling the forward and backward rotation of said support to follow the load applied by a seated user, when the rotation axis is proximate the seated user's lumbar spine. The spring 156 is attached to at least a portion of the rotary mount and biased to urge said back support surface to a substantially vertical starting point. The spring 156 then resists the seated user from reclining about the rotary or pivot axis. However, after the seated users has reclined, the energy stored in the spring 156 then assists the user in coming back to an upright posture from the reclined posture. Preferably, when a user is not seated the tension spring urges the backrest to a substantially vertical position. However, the actual orientation of the backrest from this substantially vertical starting point is preferably angularly adjustable with respect the pivot axis. It is also preferable that the vertical height of pivot axis be adjustable with respect to seat supporting the user.

Additionally, FIG. 5A illustrates the alternative embodiment wherein the threaded post 153 is now attached to the end of knob 137, and is screwed into a threaded insert in support plate 154 to secure the seat back 140 (which may or may not be cushioned) to the U-shaped support brace 130. One or more washers 161 are optionally disposed about threaded 153 adjacent to the connection with knob 137. The additional or removal of these washers 161 allows the orientation of the starting point of the backrest 140 to be angularly adjustable with respect the pivot axis, as the end of the threaded post 153 distal from knob 137 can be inserted further through the support plate 154 to urge the mounting plate 157 away from support plate 154.

Horizontal movement of back support cushion 140 is accomplished by subdividing U-shaped support brace into telescoping segments. The rear segment 138, that is connected to square plate 136, is extended from forward segment 139 by first releasing grip control knob 133 and then sliding the cushion 140 to the preferred position. In preferred embodiments, rotation of knobs 133 causes direct movement of back support cushion 140.

In further embodiments, the resistance of the cushion to reclining about the major axis is controllable via a means to increase or decrease the spring force, as well as increase/decrease the friction that resists the pivoting motion.

The chair of the instant invention is always user ready in the most preferred embodiments wherein the return springs are balanced to provide an automatic adjustment for the majority of the population, over the full range of motion of the chair and orientation of the user/worker. The mechanisms and means for adjusting the tension in the return springs associated with the seat support and back support rotation about the first rotary axis is further illustrated in FIG. 6.

In perspective view FIG. 6A, section A-A′ corresponds to FIG. 6B to show the cooperative assembly of the forked armature 110, seat return spring 610, forward portion 139 of U-shaped bracket 130 and swing arm 121′ disposed axially about shaft 650. Friction washers 615 may be disposed between opposing surfaces that rotate on shaft 650. All parts are held in place via a retaining nut 660 disposed at the end of shaft 650.

In preferred embodiments, the spring tension that resists the pivoting rotation of U-shaped bracket 130, that is the recline resistance, is adjusted by trimming the length of the springs, such as by a cam lever, screw drive and the like. As shown in FIG. 6A, the rotation of U-shaped bracket 130 is resisted by a spring 620 is retained in cup 625. Cam 630 displaces the cup 625 to modify the tension in spring 620. The initial recline resistance in the preferred embodiments can be adjusted through a range from about 1 lb. to about 30 lb. as measured by hanging a weight from knob 137, with the backrest cushion 140 in place. When the weight is hung the back support bracket 130 will rotate down approximately one degree from its starting position.

In a further embodiment of the invention, illustrated in FIG. 7, the chair includes a pivoting auxiliary support surface 710 that rotates from a position outside the gap formed by forks 110 to a position forward of pivot point 720, which is optionally a rotating shaft or rotary coupling, to a further position between the forks. In FIG. 7B the auxiliary support surface is disposed in the retracted position by rotation about pivot point 720. The auxiliary surface need not be deployed in combination with armrest 111, as shown, however, when so deployed it may be advantageous that it pivots about a common axis or point 720.

In another embodiment of the invention, illustrated in FIG. 8, armrests 111 includes an upper member 810 that is connected at one end proximate the end of plate 812 via an extended rotary coupling 811. The opposing side and opposite end of plate 812 is connected to the upper ends of the forked armature 110 via a second rotary coupling 813. The height of at least one of the shafts deployed in the first and second rotary coupling can be adjusted to raise and lower the level of the armrests with respect to seat support 120. Thus, the cooperative rotation of upper member 810 and plate 812, via the extended rotary couplings 811 and 813 provides for double pivoting movement of the armrest 11, to and between the forward position of FIG. 8A,a and the rearward position of FIG. 8B, while the upper member that makes contact with the user's forearms stays in a horizontal position independent of user's forward or backward tilt. It should be further appreciated that the frictional contact between user's forearm and arm pad with freely rotating armrest always optimizes hand position independent of forward or backward tilt. The auxiliary support surface provides ergonomically correct positioning for tools such as a keyboard, numeric pad or mouse, eliminating the need for a separate height adjustable support for such tools and/or separate forearm supports.

Thus in this preferred embodiment, in combination with the tilting movement shown in FIGS. 1B, 1C and 1D motion, the upper member 810 of armrests 111 supports the forearms of the seated user to reduce the load carried by the arms, shoulders, neck and back and cooperate with the seat and back supporting elements to maintain ergonomically correct orientation to the keyboard or work surface.

It should be understood that the term back support is intended to encompass both cushioned and non-cushioned surfaces, such as plastic, wood and mesh fabrics and the like, upon which the user's back would rest.

While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be within the spirit and scope of the invention as defined by the appended claims. 

1. A chair comprising: a) a frame having a forked armature extending upward there from, b) a seat support mounted in suspension about a first rotary axis from the forks of said frame, c) a U-shaped mounting bracket having a left and right terminus, each of which is disposed in rotary connection about the forks of the armature and in substantial coincidence with the first rotary axis, d) a back support disposed between the left and right terminals of said U-shaped back support, being mounted to pivot thereon about a second rotary axis that is located behind the back support cushion and proximate the lumbar spine region of the seated user.
 2. A chair according to claim 1 wherein the pivoting movement of said back support cushion about the second rotary axis is opposed by a spring.
 3. A chair according to claim 1 wherein the pivoting movement of said back support cushion about the second rotary axis is opposed by a tension spring.
 4. A chair comprising: a) a frame having a forked armature extending upward there from, b) a seat support mounted in suspension about a first rotary axis from the forks of said frame, c) a U-shaped mounting bracket having a left and right terminus, each of which is disposed in rotary connection about the forks of said armature and in substantial coincidence with the first rotary axis, d) at least one laterally disposed arm rests connected to the forks of the armature so as to remain in a substantially horizontally disposed position regardless of the tilt of said seat support or said back support cushion, wherein the armrest comprises a horizontally pivoting portion.
 5. A chair according to claim 4 wherein the horizontally pivoting portion of said at least one laterally disposed arm rest double pivots with free rotation.
 6. A chair according to claim 4 wherein the horizontally pivoting portion of said at least one laterally disposed arm rest comprises a pivoting auxiliary device pad.
 7. A chair according to claim 6 wherein the pivoting auxiliary device pad is tear drop shaped.
 8. A chair comprising: a) a seat support mounted above the ground, b) a back support cushion generally perpendicular to said seat support and connect thereto about a rotary axis that is located behind the back support cushion and proximate the lumbar spine region of the seated user, c) wherein the pivoting movement of said back support cushion about the second rotary axis is opposed by a tension spring.
 9. A backrest for a chair comprising: a) a back support surface, b) a rotary mount attached to said back support surface enabling the forward and backward rotation of said support to follow the load applied by a seated user, c) a spring attached to at least a portion of the rotary mount and biased to urge said back support surface to a starting point and resist a seated user reclining to rotate said back support from said starting point about said rotary mount whereby the energy stored in said spring from the rotation then assists the user in coming back to an upright posture from the reclined posture.
 10. A backrest for a chair according to claim 9 wherein the vertical height of the rotary mount with respect to a seat supporting the user is adjustable.
 11. A backrest for a chair according to claim 9 wherein the starting point of said back support surface is angularly adjustable with respect the rotary mount thereof.
 12. A backrest for a chair according to claim 10 wherein the substantially vertical starting point of said back support surface is angularly adjustable with respect the rotary mount thereof.
 13. A backrest for a chair according to claim 9 wherein the forward and backward rotation of said support follows the load applied by a seated user when the rotation axis is proximate the seated user's lumbar spine. 